Fracture toughness of tooth acrylics.

The hardness, fracture toughness, toughness, flexural strength and Young's moduli of three acrylic tooth polymers were investigated. The first polymer was based on a conventional homopolymer poly(methylmethacrylate). The second was based on cross-linked poly(methylmethacrylate) with an uncross-linked poly(methylmethacrylate) coating. The third material was based on an interpenetrating polymer network (IPN) of a cross-linked and uncross-linked poly(methylmethacrylate). All three polymers had similar hardness values. The cross-linked and IPN polymers had higher fracture toughness (K(IC)) and toughness (G(IC)) values than the conventional homopolymer poly(methylmethacrylate) polymer and lower flexural strengths (sigma(f)). The toughness of the cross-linked and IPN polymers was higher due to crack deflection around the polymer bead structure and the polymer beads acting as crack pinning sites.